While this blog post is not a definitive answer, he cites Ramba"m's statements at the beginning of Hilchot Yesodei Hatorah, pointing out how Ramba"m uses the word "Emet" in various ways that go beyond the common translation as "truth". Excerpt:
The Rambam here is not talking about what is True, but about what is
Real.
Aside from general accuracy, I think that the difference between the
different translations is profound. 'Truth' is an abstract concept
that we essentially borrowed from the Greeks. They invented or
discovered (not getting into that here) logical rules and postulates
which allowed them to categorize statements as being 'true' or
'false'. Something which is 'True' corresponds to some kind of Ideal
Form, and something which is false does not.
At some point, the Hebrew terms 'emet' and 'sheker' came to correspond
to these Greek concepts. As we got used to the Greek way of thinking,
it was important to have the vocabulary to communicate it. The problem
is obviously that it ends up 'Hellenizing' ideas and statements that
appear in early Jewish works. Those early sources are not necessarily
concerned with abstractions. The Torah and the Neviim, and Chaza"l in
their wake, are amazingly concrete, often expressing abstraction in
very 'earthy' ways. They were interested in what's real and what's
fake, what's authentic and what's phony, what's original and what's
imitation. The problem with lying is not the violation of some
abstract category, but the representation of something which is
misleadingly non-real.
As a supporting idea, you often see the term "Emet" following "Chesed", as in this week's parsha in Breishit 24:49 where Eliezer asks that Rivka's family perform "Chesed V'Emet". I encourage you to view Ibn Ezra's commentary, there. Essentially, he says that "Chessed" is something that is not required and "Emet" is something done to establish the "chesed". The point is, that Eleizer prefaces this with the word "osim" - to DO, meaning a physical, realistic act. Thus this lends support to the notion that "Emet" is based on physical reality and not just plain "vacuous" concepts of "truth" referring to things that don't exist.